A haloarchaeal ferredoxin electron donor that plays an essential role in nitrate assimilation.

Basilio Zafrilla, Rosa María Martínez-Espinosa, María José Bonete, Julea N Butt, David J Richardson, Andrew J Gates

Index: Biochem. Soc. Trans. 39 , 1844-1848, (2011)

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Abstract

In the absence of ammonium, many organisms, including the halophilic archaeon Haloferax volcanii DS2 (DM3757), may assimilate inorganic nitrogen from nitrate or nitrite, using a ferredoxin-dependent assimilatory NO₃⁻/NO₂⁻ reductase pathway. The small acidic ferredoxin Hv-Fd plays an essential role in the electron transfer cascade required for assimilatory nitrate and nitrite reduction by the cytoplasmic NarB- and NirA-type reductases respectively. UV-visible absorbance and EPR spectroscopic characterization of purified Hv-Fd demonstrate that this protein binds a single [2Fe-2S] cluster, and potentiometric titration reveals that the cluster shares similar redox properties with those present in plant-type ferredoxins.